As Proponents Look Forward to Arguments Before Justices, Foes Warn of '50-State Solution' to Issue

Less than four years ago, some gay-rights activists thought it would be a mistake to wage a Supreme Court battle over gay marriage. This week, the issue comes to the nine justices for nearly three hours of argument, and gay-marriage proponents are confident of at least a partial victory.

"I feel a little short of breath about it—it feels like we are at an incredibly important moment for our movement," said Kate Kendell, of...